The invention concerns an axial-flow blower arrangement for the condenser of an air conditioning installation to be mounted on a vehicle roof.
It is known from the state of the art, for air conditioning vehicles, in particular buses, to use roof-mounted air conditioning installations in which all components required for air conditioning are integrated.
In that respect a particular structure represents so-called one-part compact installations in which all components are mounted in a carrier or tray structure with further housing portions and casings on the vehicle roof. In general, viewed in the direction of travel, arranged to the right and the left of the center of the vehicle are evaporator trays which together with the components accommodated therein are referred to as evaporator units. With that type of installation, positioned between the evaporator units is a condenser unit which includes the condenser and the blowers required for passing air therethrough, generally axial-flow blowers. The condenser unit also connects the two evaporator units together in terms of strength-related aspects so that the three units together with the covers and casing portions afford a compact installation.
With this special construction at least one elongate, horizontally disposed condenser is used, over which is arranged an axial-flow blower air box, the areal dimension of which is at least as large as the area of the condenser. Generally a plurality of axial-flow blowers are arranged in succession in the direction of travel in those axial-flow blower air boxes in such a way that their rotary shafts extend in a vertical direction. Fitted beneath the condenser are connecting struts which connect the two evaporator units together and at the same time support the condenser. The axial-flow blower air box is also mounted to those connecting struts.
Provided between the condenser or the axial-flow blower air box and the evaporator units arranged to the left and right thereof are air flow passages which at their top side have air intake openings covered by grills. At their open underside those air flow passages open into an air collecting chamber which remains between the condenser and the vehicle roof and out of which air is sucked through the condenser by the action of the axial-flow blowers and is discharged upwardly to the external space through air outlet openings covered with grills. Air is also sucked in under the ends of the condenser, that is to say at the front and rear in the direction of travel, and flows in from various openings in the casing portions. Air is therefore supplied to the condenser over its entire periphery. Together with the spacing relative to the bus roof, that affords the suction intake area, the size of which is a substantial measurement in respect of the amount of air which can be supplied.
A disadvantage with that known arrangement is that relatively many components are required to connect the evaporator units and for mounting the condenser unit. A plurality of carrier elements which are arranged in succession in the direction of travel are required, which connect the evaporator units together and support the condenser unit. The at least one condenser of a height of more than 50 mm, the axial-flow blower air box, the axial-flow blowers themselves and the air flow passages between the axial-flow blower air box and the evaporator trays are mounted by way of those carrier elements. The weight and the costs of those components are high and they require a mounting procedure which is time-intensive. The axial-flow blower air box is relatively large and cannot be produced with favorable, off-tool processes.
That is used to denote those processes in which the component in question can be removed from a molding or shaping tool in the condition of being ready for use without subsequent further processing and the fitment of further additional parts.
Satisfactory uniform supply of air to the condenser from below upwardly depends greatly on the free flow cross-section under the condenser and the spacing of the axial-flow blower blades from the condenser. As the structural height of roof-mounted air conditioning installations is to be as low as possible because of the overall height of the vehicle and for design and weight reasons, there is generally only a comparatively small free cross-section for the intake flow of air into the condenser and the blowers whereby the amount of heat which can be transmitted is reduced.
The connecting struts extending under the condenser transversely relative to the direction of travel additionally impede the free flow of air. The axial-flow blowers which are mounted at small spacings above the upper surface of the condenser substantially only suck air out of the circular area directly beneath them. As the condenser is generally of a width greater than the diameter of the blowers it does not have air flowing uniformly therethrough both transversely relative to the direction of travel and also in the longitudinal direction. In addition upon failure of an axial-flow blower a large part of the air flow is short-circuited from the next blower and therefore does not flow through the condenser. In such a case the performance of the condenser is reduced more greatly than corresponds to the area of the failed blower.